Process for exhausting lamps.



M. M. MERRITT.

PROCESS FOR EXHAUSTING LAMPS.

APPLIGATIOH FILED JAN. 27, 1905.

909,81 1 n Patented Jan. 12, 1909.

witnesses I Luverb/Zor: am (6F WMW- J'Ia 21/. cu. p1; JJiarzu'il,

UNITED STATES PATENT ,oFFIoE;

mirrnnwai. nnaarrnor mnnnnfron, ass'renon 'ro Bos'roNmeAN DESOENT LAMP COMPANY, or nanvnas, MASSACHUSETTS, a 'cortroaarrou or mesarnoenss roe-amateurs mites.

I are. .eo9,s1i.

Specification of Letters latent.

Patented. Jan. 12, 1909.

Application filed mm 27, 1905. Serial No. 242,848.

To all who're 'it 'may concern:

Be it known that I, MATT-IIEW M. ME'R- particularly in a new process of employing a chemical assistant in the exhaustion of the bulb.

. The process of lamp exhaustion, as heretofore carried out, has consisted generally in exhausting the bulb to some selected Pa nt hy ne ,.aWe1 um..-Pump- .Th we t e t the be ated-the filament broughtto a state of high incandescence by'the passage of an abnormal ourrent therethrough to ex el the gases absorbed in"the filament an the'joints thereof and at the same time suitable chemical substances are permitted to act upon the deleterious gases, and articularl the oxygen, remainin within the bulb. heobject of this is t e conversion into harmless compounds of those gases which'remain after mechanical exhaustion in the highly'rari fied atmespli er of the .bulband would be injurious to'the' life or efli'ciency of the filamentl This 4 roc e ss of chemical exhaustion s e n e rls e'wn i h r o many years. More recently, this rocess has been practiced by msertin the c emical agent in the open ended tub ature which it is customary to secure to the tip of the bulb about to be exhausted. This tubulature havmg been connected with the pump and exhaustion carried to the required degree, which is naturally short of the final vacuum,

communication is interrupted between the pump and the tubulature below the chem- 10:11. The lamp filament is then broughtto intensive incandescence and simultaneously the chemical in the tubulature (if, as usual,

a volatile chemical is em loyedz is heated to causelitito unite with ,t 'e occ uded gases 91ithe bulb a d th ideleterioas driven F the. b n at the fil m a't. and t e joints, "Assam as chemical union has-taken place, which is-determined by the visual dis, appearance of an intensely blue or violet colored low within the bulb, the latter is sealed 0 from the tubulature above the.

chemical, the lamp then being a pra'cftically finished state.

The process of introducing a chemical agent into the tubulature has material def ir s. admit ed b fore the. c e cal action it 'co r p ted, he IQ i ly ides t -3'61. bl impaired, but the ch m c l. ti n i 'ic jmp' nied. by h pr duction of a brownish yellow de osit on the interior of the bulb which ma es the lamp. defectiveand unsala'ble. It is 'a frequent occurrence in carrying out the process described to overheat the tubulature .while volatilizing the chemical and permanently discolor the bulb. This procedure also involves the m ha hur ied se ing 91f o-i-" bulb from the tubulature while the chemical action at i height This ha y eali g i. he l i ft n e c mp n ed by the form it n bf a s gh crack a the se l, orv h'e missie f 'small amount f r for h eal. 'perfee d, h h res l s a a ei'a 'poili ig he l mp an t n mp r n g or stroy'mg the vacuum. After comp tionof mechanical exhaustion and before the chemical action takes place, much of the remnant aseous matter is in the form of moisture.

his becomes apparent to the eye in the form of an illuminated fog-like haze before the filament is brought to intensive incandescence, which haze hovers about the narrow opening between the tubulature and the bulb. Under the process referred to, it is extremely difiicult to properly extract this ical and filament, the pump tends to suck the chemical out of the tubulature while extracting the moisture in the bulb only with the greatest difficulty. This trouble is also enhanced by the fact that the tubulature throu h which or into which the moisture should pass, is raised to a high heat tending to drive back the moisture into the bulb. The final sealing of the lamp which .is performed after interrupting communication with the vpump also tends to drive an attracted or absorbed moisture in the tu ulature out of it and into the rapidly cooling and relatively cooler bulb.

Prior to the exhaustion process the bulb is customarily heated in an oven to drive off the absorbed moisture and gases. Unless the exhaustion is effected rapidly, however, the subsequent cooling of the bulb causes a mat rial re-absorption of those gases. Again, if the filament is raised to intensive incandescence without the presence of the volatilized chemical the expelled gases tend to unite with the hot filament greatly to its detriment. It is diflicult to perform the present process rapidly enough-to prevent a material cooling of the bulb, and, owing 'to-the remoteness of the chemical from the filament and the check which the expelled moisture puts upon the entrance of the chemical into the bulb when the filament is raised to intensive incandescence, a large portion of the expelled gases undoubtedly combine with the ighly heated filament, burning and blackenlng the same.

My process provides an entirely novel and different mode ofperforming the exhaustion of the lamp, whereby it can be completed with fewer steps and in less time than with the present process, being at the same time free from the defects above ointed out.

My process will be best an erstood by reference to the following description, wherein, for illustrative purposes, there is given in detail the preferred mode of performing it, while its scope will be more particularly pointed out in the appended claims.

The drawing shows diagrammatically a lamp bulb a with its contained filament b and the attached tubulature c, all of which are typical of a lamp of the usual construction. The end of the tubulature is shown inserted in a rubber socket connection 01, which is in communication with an air pump (not shown). The latter may be of any description capable of exhausting to the degree required as a preliminary for the chemical action.

Preferably within the normal bulb space, instead of in the tubulature as before, and preferably, although not necessarily, upon the inner walls of the bulb itself, as at 6, there is deposited a small and preferably definite amount of some one of the wellknown agents suitable for chemical exhaustion, such, for example, as .red amorphous phosphorus. The location of the chemical.

shown in the drawing, is particularly advantageous, for it-is in immediate proximity to the porous pasted joints of the filament wherein are absorbed the major 01- tion of the deleterious gases finally expe led. The insertion of this chemical (which in the drawing is shown greatly exaggerated in amount) is effected at some prior stage in the process of the lamp manufacture and may be conveniently accomplished before the tubulature is joined to the bulb. The lamp having been previously warmed or heated, as in an oven, to drive out as large a portionas possible of the absorbed gases, its tubulature is connected with the pump, as shown in the drawing, and there remains for a few moments until mechanical exhaustion to the required degree has been accomplished. Meanwhile the filament may be made to glow sllghtly by the passage therethrough of a current of normal or somewhat less than normal strength. This point having been reached, I then preferably bring the filament to intensive incand'escence and at the same time heat the glass bulb, and particularly at the point e where lies a deposit of chemical, the connection with the pump, however, preferably remaining uninterrupted. This volatilizes a portion of the chemical already within the bulb, causing it to act, not only upon the residual gases of the bulb space, but also upon the expelled ases from the filament and the joints thereof andthe gases driven out from the pores of the bulb, these gases, however being freed in the immediate presence 0 the volatilized chemical and having no op- I portunity to unite chemically with the filament. The heat applied to the bulb to volatilize the chemical also materially assists in expelling the absorbed gases. During this operation the pump easily withdraws the moisture discharged from the filament and the bulb through the free open passage of the tubulature which is obstructed by neither volatilized nor unvolatilized chemical.

As soon as the moisture has been withdrawn and before the chemical has been completely volatilized, the lamp is sealed between the bulb and the tubulature at f, such sealing hermetically closing both the bulb and the tubulature, which latter remains in the socket. The chemical remaining within the bulb, which latter is now in its complete, hermetically-sealed state, is then again heated to complete'its volatilization and the filament simultaneously brought to intensive incandescence. This operation will be 1 accompanied first by the appearance and then the disappearance of the blue glow referred to, which will indicate the completion of the exhaustion of the lamp. The

severed and sealed tubulature may remain hausted, when it may be replaced by the tubulature attached thereto. It will be seen that the final step of this process of exhaustion, as here performed, is the chemical action upon the atmosphere of the bulb after the latter is hermetically sealed in its completed state and after every step which can in any way affect the vacuum therein has been performed. This absolutely avoids the possibility of any air or gases entering into the bulb during the final chemical action. It also permits this final chemical exhaustion to be ,carried on carefully and, if desired, leisurely. In, fact, any desired interval may elapse between the time of sealing of the bulb and the time of volatilizing the remaining chemical in the presence of the incandescent filament.

The present process requires the placing of an amount of chemical in the tubulature largely in excess of what is required for the actual chemical action which takes place. This is not only detrimental because the chemical absorbs and retains a considerable quantity of moisture, but more particularly because it is diflicult or impossible for the operator to volatilize just the precise amount needed for the required chemical reaction. This required amount is a definite quantity and if exceeded will result in a discoloration of the bulb similar to that produced when air is admitted in excess through an accidental crack or fissure, as above described. The use .of an excess J amount of chemical, however, is anecessary consequence of its volatilizationin the tubulature, for it is volatilized at a point-comparatively remote from where it is needed and an indeterminate portion of it undoubtedly fails to enter the bulb at all. By my process, the amount of chemical can be reduced to substantially that which is required for the chemical action, this being a definite proportion which can be easily determined'in each case. When this is volatilized it may be known that the action is cooling of the bulb. As

moment of sealing the bulb, so that allmoisture and gaseous matter which it is possible for the pump to withdraw will be withdrawn without interference oropposition on the part of the volatilized chemical.

The mani ulation-in my process is so simplified that it can be performed with eater rapidity, and with less 0 porthnity or the liasbeen observed, however, the latter is no serious defect in my process for the heating of thechemical is accompanied by a heating of the bulb and the expulsion of the contalned gases in the immediate presence of the chemical.

Other advantages, many of which will be apparent to those skilled in the art, follow from the use of my rocess but these, as well as the many modifications thereof and the many variations in the detailed steps thereof are unnecessary to mention; it being understood that my invention is not limited to the details here described but only to the broad principles claimed.

Claims: 1. The process of exhausting lamp bulbs which consists in inserting a volatile chemical agent within the bulb, placing the latter in communication with a ump, exhausting to the required degree, raising the filament to a state of incandescence and partially volatilizing the said chemical while said bulb is still in communication with the pump, sealing off the bulb and thereafter completing the volatilization of the chemical in the presence of the incandescent filament.

' 2. The .process of exhausting a lamp bulb which consists in placing the latter in communication with a pump, exhausting to the required degree, raising the filament to a state of incandescence, acting upon the re- MATTHEW My MERRITT.

Witnesses:

CHARLES E. Pmncn, THOMAS B. BooTH. 

